Resin casting - what clay to use for molds?

adamata

Sr Member
RPF PREMIUM MEMBER
What is the best clay to use for making RTV molds? (IE what you fill in the bottom of the mold box to make the top half of a two-part mold)

I have tried a few things with very little success.

what have you guys used?
 

Darth Domain

Well-Known Member
<div class='quotetop'>(adamata @ Jun 14 2006, 08:25 PM) [snapback]1261659[/snapback]</div>
What is the best clay to use for making RTV molds? (IE what you fill in the bottom of the mold box to make the top half of a two-part mold)

I have tried a few things with very little success.

what have you guys used?
[/b]
This site should answer your question, they have a forum to, they are very helpful

http://www.alumilite.com/
 

propsculptor

Sr Member
RPF PREMIUM MEMBER
I use Leisure Clay, it works well with anything and won't react to any materials,
such as Plastics or Silicones.
 

LeMarchand

Sr Member
i use the kind of clay you buy for kids. It comes in all those happy colors and doesn't dry out and it doesn't react with silicones.

Marc
 

Macklin

Well-Known Member
I use Play-Doh.

It doesn't react, sticks to absolutely nothing and is super cheap.

It's not good for every use out there, but it's great for small parts.
 

SG Merc

Well-Known Member
As all of the above posts basically say, use a wax based clay that doesn't have any sulfur in it.

I use an art clay from the craft store. It works the same as Kleen Klay, but ends up costing half the price (with shipping from Mirco Mark etc..).
 

Ghost Host

Sr Member
You can use most anything, but I know many FX professionals use WED clay. it's a water based clay made for things such as this.
 

GuntahKela

Sr Member
I use the green Roma Plastilina bought at art supply stores. Have had my batch for 12 years, and it still works fine.
 

modelnutz

Member
I'm one of those that uses WED clay.
More specifically, Laguna brand from michaels.
$6.00 a box.
The gray type is better than the terra cotta...less stickyness.
Cleans up with water.
 

exoray

Master Member
I'm one of those that uses WED clay.
More specifically, Laguna brand from michaels.
$6.00 a box.
The gray type is better than the terra cotta...less stickyness.
Cleans up with water.
I use WED as well, from Hobby Lobby, Amaco X-15 potter clay... 25 pound box, normal price is $14.99 but they have 40% coupons almost every week on the website so I only pay $9 a box, and I avoid shipping cost...

The only issue with the X-15 is that it's not advertised as sulfur free so it would be wise to test your batch first... But, I have used it for several years (multiple batches) for both tin and platinum cure silicone without issue...

The reason I use WED is simply because it's cheap and I can get it local easily... And the fact that I'm lazy, and prefer to use it once and then simply toss it and get a new batch for the next project, no time spent trying to reclaim it...

The oil and wax based clays like mentioned above have the advantage that they don't dry out and are easy to reclaim and re-use but they are more costly from the start... They also don't shrink like WED clays, not an issue if you mold right away but if you leave WED exposed to the air for even a few hours it will start to dry out and shrink, and pull away from the object...

That new elastic Monster Clay looks very interesting, I might have to pick some up and play with it...
 

division 6

Master Member
Does the moisture in the WED clay effect the silicon or does it need to be sprayed with a coat of lacquer?
 

EricHart

Member
If you ever try a new clay, and it turns out to have sulfur in it, or some other chemical which inhibits your silicone from curing, you may still be able to save your pouring. Remove the clay from the silicone, and let the layer of uncured silicone remain exposed to the air for a few hours; sometimes that's enough for it to fully cure.
 

Little Fett

Member
I use everyday water based for my silicone molds. The texture gets alittle funky in places though (not due to chemical reaction, just the fact that it really captured the exact texture of the clay), so you might wanna go with something alittle more high quality.

I swear by water based though, but that's probably because I'm just cheap:love.
 

exoray

Master Member
Does the moisture in the WED clay effect the silicon or does it need to be sprayed with a coat of lacquer?
I have never experienced any adverse results due to the moisture... I never deliberately coat it with any type of sealer, although depending on the part being molded I might dust it with some paraffin release and that inevitably over sprays onto the clay...

If it has sulfur it in though you could run into some big issues, some tin cure silicone will rough it out and do just fine with sulfur, but not all... And IMO forget about any platinum cure and sulfur, big gooey mess just waiting to happen...
 
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